using PCI7344's digital I/O to control steppers?

[langtian]

There is no need to control the speed of the steppers,so i want to use  the digital I/O  on 7344 to control the steppers.

Is it possible? any suggestion about it?

Thanks for your answer!

[Jochen]

The digital I/Os on a PCI-7344 are static I/Os and can't be used for controlling a stepper in a reasonable way. The DIOs can be turned on and off in software only, the maximum speed is not more than 100 Hz and  there will be a high amount of jitter, too so I wouldn't waste any time for this experiment as you probably won't get acceptable results.

What's the reason for this question? Do you need to control more than 4 axes? If not I would highly recommend using the designated stepper control circuitry of the board.

Best regards,

Jochen Klier
National Instruments Germany

[langtian]

I need to control 3 servo motors, and i bought one 7344

I also need to control more than 7 steppers whose speeds are some constants.  I thought I can control them through digital I/O on 7344,but you denied it. I now consider to control them through 6221,do you think it will be ok to make it run smoothly. I'm not intent to use 7358 because it is a little dear.However if you suggest me that 6221 is not a good choice, I think i would change it.

Thanks a lot

帖子被langtian在12-21-2005 08:18 PM时编辑过了

[Jochen]

As the 6221 provides hardware timed digital I/Os theoretically the board could be used for this task. On the other hand it's not possible to send the pulse trains for each axis independently to the digital outputs. That means you would have to calculate a single digital waveform containing all the pulse trains for the axes. This will become very complicated and inflexible.

The money that you could save with the lower price of the 6221 will be dissipated by the additional working hours you will have to spend to program this solution. Additionally NI motion control boards provide security features like onboard monitoring of limit switches and following errors (closed loop only) which can't be provided by the 6221.

I highly recommend using NI motion control boards instead of a DAQ board. If there are enough PCI slots left you could use this board configuration to save some money:

1 x PCI-7344:   3 servos, 1 stepper
1 x PCI-7334:   4 steppers
1 x PCI-7332    2 steppers

= 3 servos + 7 steppers

Best regards,

Jochen Klier
National Instruments Germany

Best regards,

Jochen Klier
National Instruments Germany